Device and method for the geometric determination of electrical dipole densities on the cardiac wall

ABSTRACT

Disclosed are devices, a systems, and methods for determining the dipole densities on heart walls. In particular, a triangularization of the heart wall is performed in which the dipole density of each of multiple regions correlate to the potential measured at various locations within the associated chamber of the heart.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 15/882,097 filed on Jan. 29, 2018, which is acontinuation application of U.S. patent application Ser. No. 15/333,378filed on Oct. 25, 2016, now U.S. Pat. No. 9,913,589 issued Mar. 13,2018, which is a continuation application of U.S. patent applicationSer. No. 14/886,449 filed on Oct. 19, 2015, now U.S. Pat. No.9,504,3s95, issued Nov. 29, 2016, which is a continuation application ofU.S. patent application Ser. No. 13/946,712 filed on Jul. 19, 2013, nowU.S. Pat. No. 9,192,318, which is a continuation application of U.S.patent application Ser. No. 12/836,411, filed on Jul. 16, 2010, now U.S.Pat. No. 8,512,255, which is a 371 national stage application of PatentCooperation Treaty Application No. PCT/IB2009/000071 filed Jan. 16,2009, entitled A DEVICE AND METHOD FOR THE GEOMETRIC DETERMINATION OFELECTRICAL DIPOLE DENSITIES ON THE CARDIAC WALL, which in turn claimspriority to Swiss Patent Application 00068/08 filed Jan. 17, 2008, eachof which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the localization andtreatment of cardiac arrhythmias, and more particularly to devices andmethods for the geometric determination of electrical dipole densitieson the cardiac wall.

BACKGROUND

Systems used to localize the origin of cardiac arrhythmias measurepotentials (e.g. in millivolts) in the cardiac chambers and localizethem on a three dimensional representation of the cardiac chamber wall.The measurement of the electrical activity present on the cardiac wallsis called mapping. For this purpose, a multiple electrode mappingcatheter may be positioned within the heart such that multiplepotentials can be simultaneously measured at different locations on thewall of the cardiac chamber without having direct wall contact(non-contact mapping). The cardiac chamber is visualized as a threedimensional structure, either directly by moving one or more mappingelectrodes within the corresponding heart chamber or by importing ananatomical geometry of the cardiac chamber from an imaging device (e.g.Computed Tomography, MRI, or ultrasound). The electrical activity withinthe heart can be measured with the multi-electrode mapping catheter,which may be able to simultaneously measure potentials at differentpoints in three dimensional space. In the current systems, the measuredpotentials from the non-contact multi-electrode mapping catheter do notdirectly correspond to the electrical activity on the cardiac wall asmeasured with an electrode with direct wall contact (contact mapping).The measured potentials of the non-contact mapping system have to beconverted with computer programs and extrapolated into virtualelectrograms projected on the heart chamber of the mapping system.

The current conversion methods are inaccurate, and further processing,termed regularization methods, have to be used. These regularizationmethods decrease spatial resolution. Another limitation of the currentmethods is that the provided potentials represent only the meanelectrical activity that emanates from different cells, consisting ofmembranes separating electrical dipoles.

Since the localization of cardiac arrhythmias by the use of potentialsis imprecise, the successful treatment of cardiac arrhythmias has beendifficult and has demonstrated limited success and reliability. Thereis, therefore, a need for improved methods of localizing cardiacarrhythmias.

SUMMARY OF THE INVENTION

Several unique devices, systems, and methods for creating a database ofdipole densities at a surface of a patient's heart are provided. Dipoledensity information can be used by a clinician to diagnose and treatheart diseases such as arrhythmias. The dipole density information isbased on anatomical models of the patient's heart and mappinginformation recorded by multiple electrodes, such as electrodes includedon the distal end of a three dimensional mapping catheter.

According to a first aspect of the invention, a device for creating adatabase of dipole densities at the surface of one or more cardiacchambers of a patient is provided. The device includes a first receiverthat receives mapping information from multiple electrodes included inone or more mapping catheters. The electrodes are placed in a cardiacchamber of the patient's heart. The device further includes a secondreceiver that receives anatomical information. The anatomicalinformation may be a generic heart model, or more preferably tissuecontour and other anatomical information recorded from the patient's ownheart. A dipole density module determines the database of dipoledensities, in the table form d(y), where y represents the location onthe heart tissue including that particular dipole density. The potentialat various locations x, within a cardiac chamber and termed V(x), arerecorded by the multiple electrodes. Solid angle {acute over (w)}(x,y)represents the solid angle for a triangle projection between location x(electrode location in chamber) and y (triangle location on chamberwall). The dipole density module determines the dipole density forindividual triangle shaped projections onto the cardiac chamber wallbased on the following: each triangle projection at location ycontributes {acute over (w)}(x,y) times the dipole density d(y) to thepotential V(x) at the point x.

In a preferred embodiment, the device comprises a software program,e.g., such as a software program loaded onto a personal computer; an ECGsystem; a cardiac tissue ablation system and/or an imaging system. Thenumber of triangles determined by the dipole density module issufficiently large (triangle area small enough) such that the dipoledensity for each triangle projection is relatively constant. Typically1000 or more triangles are used in the calculations, such as acalculation based on a standard sized Left Atrium. Larger numbers oftriangles are used for larger sized chambers.

In another preferred embodiment, the patient is being diagnosed and/ortreated for a heart condition, such as an arrhythmia. The electrodes areincluded at the distal end of one or more mapping catheters and areplaced into a chamber of the patient's heart to record potentials. Animaging instrument, such as an instrument that provides a generic modelof a heart, or an instrument which provides an anatomical model of thepatient's heart, delivers the anatomical information to the secondreceiver. In a preferred embodiment, the imaging instrument is one ormore of: Computed Tomography; MRI; ultrasound; and an ECG system withmapping catheter.

In another preferred embodiment, the dipole density module implements analgorithm configured to assist in the creation of the database of dipoledensities. The algorithm may be a progressive algorithm configured to bemodified or refined to improve spatial and/or time resolution of thedatabase. The dipole density module may determine a map of dipoledensities at corresponding time intervals. A synthesis of mapsrepresents a cascade of activation sequences of each corresponding heartbeat.

In another preferred embodiment, the device includes a third receiver.The third receiver receives mapping information from one or more skinelectrodes. The dipole density module uses the skin electrode signals tocalculate or recalculate the database of dipole densities, usingequations listed herebelow.

According to another aspect of the invention, a system for creating adatabase of dipole densities at the surface of one or more cardiacchambers of a patient's heart is provided. In addition to the device ofthe present invention, the system includes one or more of a multipleelectrode catheter; an imaging instrument; an ablation device; and atleast one surface or skin electrode. In a preferred embodiment, themapping catheter is also used for ablating tissue identified by thedatabase of dipole densities. The system includes a monitor to displaythe dipole density information, such as information displayed inrelative geometry to the chamber of the patient's heart.

According to another aspect of the invention, a method of creating adatabase of dipole densities at the surface of one or more cardiacchambers of a patient's heart is provided. The method can be used todiagnose and/or treat cardiac disease. In a preferred embodiment, themethod is used to diagnose and treat Atrial Fibrillation (AF). Inanother preferred embodiment, the method is used to detect ventricularischemia and/or quantify myocardial function. The method includesplacing an array of multiple electrodes within a chamber of thepatient's heart to measure potentials. The array of multiple electrodesmay or may not be repositioned to determine dipole densities.

In another preferred embodiment, the method further includes placing oneor more skin electrodes. The information recorded by the skin electrodesis used to determine the database of dipole densities.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate various embodiments in accordancewith the present invention, and, together with the description, serve toexplain the principles of the invention. In the drawings:

FIG. 1 illustrates a schematic view of an embodiment of a device fordetermining a database table of dipole densities d(y) of at least oneheart chamber, consistent with aspects of the present invention.

FIG. 2 illustrates a flow chart of an embodiment of a preferred methodfor determining a database table of dipole densities of at least oneheart chamber, consistent with aspects of the present invention.

FIG. 3 illustrates a schematic view of an embodiment of a system fordetermining a database table of dipole densities of at least one heartchamber with help of the solid angle {acute over (w)}(x,y), consistentwith aspects of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the embodiments in accordancewith aspects of the present invention, examples of which are illustratedin the accompanying drawings. Wherever possible, the same referencenumbers will be used throughout the drawings to refer to the same orlike parts.

A device for calculating surface charge densities has been described indetail in PCT International Application Number PCT/CH2007/000380(hereinafter the ‘380 Patent Application) naming Scharf as investor,filed Aug. 3, 2007, and entitled METHOD AND DEVICE FOR DETERMINING ANDPRESENTING SURFACE CHARGE AND DIPOLE DENSITIES ON CARDIAC WALLS, and isincorporated by reference herein in its entirety. The present inventionprovides an improved device, system and method for calculating andvisualizing the distribution and activity of dipole charge densities ona cardiac wall. The dipole densities are directly determinedgeometrically, avoiding the errors encountered using previousextrapolation algorithms.

In accordance with the present invention, provided is a device thatmeasures and calculates a database of dipole densities d(y) on thecardiac wall. The actual measured potentials in the heart result fromelectrical activity of cells, which can be regarded as dipoles. Thedipoles consist of ion charges on both sides of biological membranes.The use of dipole densities offers a precise representation of theelectrical activity. Systems and methods in accordance with the presentinvention efficiently and effectively calculate the dipole densitiesutilizing one or more mathematical theorems. This calculation issignificantly more precise than calculations of virtual potentialsproduced by current systems, which lose spatial precision because of therequired numerical methods and the use of potentials instead of dipoledensities. Systems and methods in accordance with the present inventionare efficient in calculating dipole densities geometrically, such asthrough the use of computer systems, or similar microcontroller and/ormathematical processing equipment.

Definitions. To facilitate an understanding of the invention, a numberof terms are defined below.

As used herein, the terms “subject” and “patient” refer to any animal,such as a mammal like livestock, pets, and preferably a human. Specificexamples of “subjects” and “patients” include, but are not limited, toindividuals requiring medical assistance, and in particular, patientswith an arrhythmia such as atrial fibrillation (AF).

As used herein, the term “solid angle” is the angle subtended by atriangle on the heart wall at the position x of observation. When viewedfrom location x, straight lines are drawn from point x to the boundariesof the triangle, and a sphere is constructed of radius r=1 with centerof x. The straight lines then define the spherical triangle on thesurface of the sphere. The solid angle is proportional to the surfacearea of the projection of that object onto a sphere centered at thepoint x.

The methods and devices of the present invention have advantages overprevious prior art devices. FIGS. 1-3 illustrate various preferredembodiments of devices, systems and methods in accordance with aspectsof the present invention. However, the present invention is not limitedto these particular configurations.

Referring now to FIG. 1, a schematic view of an embodiment of a devicefor determining a database table of dipole densities of at least oneheart chamber of a patient is illustrated. Device 100 includes a firstreceiver 110 configured to receive electrical potentials from a separatedevice, such as a device including a multi-electrode mapping catheterplaced in the circulating blood within a chamber of the patient's heart.Device 100 further includes a second receiver 120 configured to receivecardiac geometry information (e.g. the geometric contour of the cardiacchamber wall), such as from an instrument including, but not limited to:Computed Tomography; MRI; Ultrasound; a multi-electrode mappingcatheter; and combinations of these. Alternatively, a standard geometrycan be loaded representing a model of the cardiac chamber. Device 100further includes a dipole density module 130 which comprisesmathematical processing element, such as a computer or other electronicmodule including software and/or hardware for performing mathematical orother calculations. Dipole density module 130 receives mappinginformation from first receiver 110 and cardiac geometry informationfrom second receiver 120. Dipole density module 130 preferably uses oneor more algorithms to process the received mapping and geometryinformation to produce a database table of dipole densities.

The geometrical model of the cardiac chamber is processed by dipoledensity module 130 into multiple small triangles (triangularization).When the triangles are sufficiently small, the dipole density at eachtriangle can be regarded as constant. In a preferred embodiment, astandard cardiac chamber of 4-6 cm diameter is divided up into over 1000triangles. In another preferred embodiment, the number of trianglesdetermined by dipole density module 130 is based on the size of theheart chamber. With the electrodes positioned in a cardiac chamber by aclinician, such as an electrophysiologist, the potentials at eachelectrode are recorded. Each triangle is seen by the correspondingelectrode under a certain solid angle. The dipole density module 130computes the solid angle {acute over (w)}(x,y) subtended by eachtriangle at position y on each electrode at position x on themulti-electrode catheter. If the dipole density at the triangle is d(y),the triangle contributes {acute over (w)}(x,y) times d(y) to thepotential V(x) at the position x on the multi-electrode catheter. Thetotal measured potential V(x) is the sum resulting from all thetriangles. A detailed description is provided in reference to FIG. 3herebelow.

In a preferred embodiment, dipole density module 130 implements aprogressive algorithm that can be modified and/or refined in order toimprove spatial and/or time resolution of the database of dipoledensities that are produced. The dipole densities d(y) are obtained bysolving a linear system of equations. This calculation requires somecare to avoid numerical instabilities. Thereby a map of dipole densitiescan be created at each corresponding time interval. The synthesis of themaps generates a cascade of the activation sequence of eachcorresponding heart beat that can be used to define the origin of theelectrical activity, arrhythmias or diagnose cardiac disease.

The measuring electrodes used in the present invention are placed in theblood flow in a heart chamber, a relatively homogeneous condition, suchthat the mathematical analysis of the present invention is wellapplicable. In a preferred embodiment, skin electrodes are alsoimplemented such that dipole density module 130 can use the informationreceived from the skin electrodes to calculate and/or recalculate thedipole densities for the cardiac wall. The spatial resolution which canbe obtained by invasive (i.e., placed in the heart chamber)multi-electrode potential measurements is limited by the number ofelectrodes that can be placed in any cardiac chamber, such as the LeftAtrium (LA). Skin placed electrodes, such as electrodes placed on thethorax, are not as space limited. However, due mainly to theinhomogeneous structure of the body, it is difficult to localize theactual sources of the skin electrode measured potentials. A highlycomplicated boundary value problem must be solved with boundaryconditions that are poorly known, and previous attempts at determiningthe “action potential” from body surface ECG (alone) have not been verysuccessful.

The badly defined boundary value problem can be avoided by an additionalmeasurement (in addition to the skin electrode measurements) of themulti-electrode array of the present invention. A small sinusoidalvoltage V_(I) is applied to each electrode I=1, . . . . . L on theelectrode array in the heart, and the resulting voltages W_(k,k)=1, . .. . K is measured at the surface electrodes. This yields the K×Ltransition matrix A_(kl)

$\begin{matrix}{W_{k} = {\sum\limits_{l = 1}^{L}{A_{kl}{V_{l}.}}}} & (1)\end{matrix}$

Calculating solid angles produces the linear transformation B_(In)between the electrode array potentials V_(I) and the dipole densitiesd_(n,)n=1, . . . N of N regions of the heart wall:

$\begin{matrix}{V_{l} = {\sum\limits_{n = 1}^{N}{B_{l\; n}{d_{n}.}}}} & (2)\end{matrix}$

N is chosen to be N=K+L where K is the number of surface electrodes andL is the number of internally placed array electrodes.

Substituting equation (2) into (1) we have:

$\begin{matrix}{W_{k} = {\sum\limits_{l = 1}^{L}{\sum\limits_{n = 1}^{N}{A_{kl}B_{l\; n}{d_{n}.}}}}} & (3)\end{matrix}$

Therefore, by simultaneous measuring of the potentials of the cardiacactivity with all K+L electrodes, N=K+L dipole densities of N regions onthe heart wall can be calculated. This method yields a higher spatialresolution than the L array electrodes alone. In the solution of thelinear system of equations (2)+(3), regularization techniques must beused (e.g. Tikhonov regularization and its modifications) in order toavoid numerical instabilities.

Referring now to FIG. 2, an embodiment of a preferred method fordetermining a database table of dipole densities of at least one heartchamber of a patient is illustrated. In Step 10, a multi-electrode arrayis placed within the corresponding heart chamber. In Step 20, thegeometry of the corresponding heart chamber is obtained in relation tothe multi-electrode array position, such as by moving around a secondmapping electrode or by importing a geometry model from an imaging study(e.g. using computed tomography, MRI or ultrasound before or after themulti-electrode array of electrodes has been placed in the heartchamber). The surface of the geometry of the corresponding heart chamberis divided into small triangles, typically at least 1000 smalltriangles.

In Step 30, the dipole density d(y) can be calculated from the measuredpotential values and the calculated solid angles. The measurements canbe repeated successively during the cardiac cycle giving a high timelyresolution during each millisecond. The information of the timelydependent dipole densities can be depicted as an activation map of thecorresponding heart chamber for the given heart beat. The informationcan be used to diagnose and/or treat a patient with a cardiacarrhythmia, such as an atrial fibrillation patient.

In a preferred embodiment, the information is used to determine cardiacwall treatment locations for lesion creation, such as a lesion createdin the Left or Right atrium, by an RF, ultrasound or cryogenic ablationcatheter. In another preferred embodiment, the multiple electrodemapping array is placed in a ventricle and the dipole densities aredetermined for the ventricular wall, such as to detect ischemia orquantify myocardial function.

Referring now to FIG. 3, an embodiment of a system for determining adatabase table of dipole densities of at least one heart chamber of apatient is illustrated. System 500 includes device 100, which isconfigured to create a database table of dipole densities d(y) based onvoltage potential measurements within the heart chamber and imageinformation relating to the heart chamber, as has been describedhereabove. System 500 further includes imaging unit 220, which isconfigured to provide a two or three-dimensional image of the heartchamber to device 100. Imaging unit 220 may perform at least one ofComputed Tomography, MRI and/or ultrasound imaging. Imaging unit 220 mayproduce any form of real or virtual models of the cardiac chambers, suchthat a triangularization analysis is possible.

System 500 further includes mapping catheter 310, which includes shaft311, shown inserted into a chamber of a patient's heart, such as theLeft Atrium (LA). At the distal end of shaft 311 is an electrode array315 including multiple electrodes 316. Electrode array 315 is shown in abasket construction, but numerous other constructions can be usedincluding multiple independent arms, spiral arrays, electrode coveredballoons, and other constructions configured to place multipleelectrodes into a three-dimensional space. In a preferred embodiment,any catheter with a three-dimensional array of electrodes can be used tosupply the mapping information to device 100.

In this embodiment, electrodes 316 are connected to wires, not shown,but traveling proximally to cable 317, which is electrically connectedto a mapping unit 210, such as an electrocardiogram (ECG) unit. ECG unit210 includes a monitor for displaying information, such as thepotentials recorded by electrodes 316, as well as the dipole densityinformation produced by device 100. In an alternative embodiment, device100 further includes a monitor, not shown, but configured to display oneor more of: dipole density information; potentials recorded byelectrodes 316; and cardiac chamber contours and other geometryinformation. In a preferred embodiment, dipole density and or recordedpotentials information is shown in reference to a three-dimensionalrepresentation of the heart chamber into which catheter 310 is inserted.In an alternative embodiment, imaging unit 220 may include a deviceconfigured to create an image of the cardiac chamber from signalsrecorded from an electrode catheter, such as catheter 310.

System 500 may include a device for treating a cardiac arrhythmia, suchas ablation source 230, which is electrically attached to electrodes 316via cable 318. Alternatively or additionally, ablation source 230 can beattached to a different ablation catheter, such as a single or multipleablation element catheter configured to deliver ablation energy such asRF energy, cryogenic energy, or other tissue disrupting energy.

As shown in FIG. 3, triangle T1, defined by device 100, is at locationY. Electrode 316 a of catheter 310 is at location X. The geometricrelationship between triangle T1 and Location X is defined by the solidangle, angle {acute over (w)}(X,Y). Device 100 includes dipole densitymodule 130 such that each triangle at location y contributes {acute over(w)} (x,y) times the dipole density d(y) to the potential V(x) at theposition x on a multi-electrode. Solid angle {acute over (w)}(x,y), asdefined above, corresponds to the triangle at a location y and theelectrode at positions x on the multi-electrode array. The dipoledensity module 130 of device 100 determines from the total measuredpotential V(x), which is the sum resulting from all the trianglesdefined by device 100, the desired dipole density d(y).

When sufficient potentials values V(x) are measured (e.g. from 10 to10,000 with increasing number of measured potentials providing moreaccurate results), the dipole density d(y) at many equally distributedregions y on the cardiac wall is calculated by solving a linear equationsystem. By interpolation of the measured potentials (e.g. with help ofsplines) their number can be increased to a higher number of regions.The solid angle {acute over (w)}(x,y) of a region is the sum of thesolid angles of the individual triangles in the region on the cardiacwall. This calculation of dipole density results, such as via anautomatic computer program forming at least part of dipole densitymodule 130.

In a preferred embodiment, the results are presented in a visual,anatomical format, such as depicting the dipole densities on a geometricimage of the cardiac wall in relation to time (t). This format allows aclinician, such as an electrophysiologist, to determine the activationsequence on the cardiac wall, such as to determine treatment locationsfor a cardiac arrhythmia. The results may be shown on a display ofmapping unit 210, or on a separate unit such as a display included withdevice 100, display not shown but preferably a color monitor. In apreferred embodiment, the device of the present invention is implementedas, or includes, a software program that is executable by at least oneprocessor. The software program can be integrated into one or more of:an ECG system; a cardiac tissue ablation system; an imaging system; acomputer; and combinations of these.

In a preferred embodiment, the multi-electrode catheter includes atleast 10 electrodes, configured to represent a three dimensional bodywith known geometry. The electrodes are preferably positioned in aspherical geometry, such as a spherical geometry created in a basketcatheter. Elliptical electrode array geometries may be used, such asthose provided in the Ensite Array Catheter, manufactured by St. JudeMedical of St. Paul Minn. In an alternative embodiment, multiplecatheters are inserted into the heart chamber to provide the multipleelectrodes.

In an alternative embodiment, the electrodes of the multi-electrodemapping array are repositioned during the method of determining dipoledensities. Repositioning of electrodes can be beneficial to increase thenumber of measured potential values, if electrode positions are known.Therefore, repositioning is in concordance with adjustment of thegeometry map in relation to the multi-electrode mapping catheter.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theembodiments disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims. In addition,where this application has listed the steps of a method or procedure ina specific order, it may be possible, or even expedient in certaincircumstances, to change the order in which some steps are performed,and it is intended that the particular steps of the method or procedureclaims set forth herebelow not be construed as being order-specificunless such order specificity is expressly stated in the claim.

1. (canceled)
 2. A system for generating a database of dipole densities d(y) at the surface of one or more cardiac chambers of a patient, comprising: an electrode array including multiple electrodes for insertion into a cardiac chamber of a patient; at least one skin electrode; a receiver configured to record mapping information from the electrode array and the at least one skin electrode; and a dipole density module configured to create a database of dipole densities d(y) at the surface of the cardiac chamber based on mapping information and a geometrical depiction of the cardiac chamber.
 3. The system according to claim 2, wherein the database of dipole densities d(y) includes dipole density information for individual triangle-shaped projections onto the cardiac chamber wall.
 4. The system according to claim 3, wherein the number of triangle-shaped projections is chosen such that the dipole density d(y) of each triangle-shaped projection is substantially constant.
 5. The system according to claim 3, wherein the number of triangle-shaped projections is at least 1,000.
 6. The system according to claim 3, wherein each triangle-shaped projection at a location y contributes {acute over (w)}(x,y) times the dipole density d(y) to a potential V(x) at a point x, wherein {acute over (w)}(x,y) is the solid angle for that triangle projection, and where: a) x represents a series of locations within one or more cardiac chambers; and b) V(x) is a measured potential at point x, said measured potential recorded by the multiple electrodes.
 7. The system according to claim 2, wherein the electrode array includes a three-dimensional array of electrodes.
 8. The system according to claim 2, wherein the dipole densities of the database d(y) of dipole densities are mapped to the one or more surfaces of the one or more cardiac chambers.
 9. The system according to claim 8, wherein the dipole density module is further configured to create two or more maps of the dipole densities d(y), and wherein each of the two or more maps are at different time intervals.
 10. The system according to claim 9, wherein the dipole density module is further configured to synthesize the at least two maps of dipole densities d(y) at different time intervals to create an activation sequence of cardiac activity over a plurality of time intervals.
 11. The system according to claim 2, wherein the dipole density module is further configured to update the database of dipole densities d(y) at a plurality of time intervals during cardiac activity.
 12. The system according to claim 11, wherein the plurality of time intervals includes at least one time interval per cardiac cycle.
 13. The system according to claim 11, wherein the plurality of time intervals includes a plurality of time intervals per cardiac cycle.
 14. The system according to claim 11, wherein the plurality of time intervals includes a time interval of about a millisecond.
 15. The system according to claim 2, wherein the multiple electrodes of the electrode array are included in a single catheter.
 16. The system of claim 2, wherein the dipole density module is configured to calculate and/or recalculate the dipole densities d(y) using the following equations: $\begin{matrix} {W_{k} = {\sum\limits_{l = 1}^{L}{A_{kl}{V_{l}.}}}} & (1) \end{matrix}$ wherein a small sinusoidal voltage V_(I) is applied to each electrode l=1, . . . . . L on the electrode array in the heart, and the resulting voltages W_(k), k=1, . . . . K is measured at the surface electrodes, which yields the K×L transition matrix A_(kl); $\begin{matrix} {V_{l} = {\sum\limits_{n = 1}^{N}{B_{l\; n}{d_{n}.}}}} & (2) \end{matrix}$ wherein calculating solid angles produces the linear transformation B_(In) between the electrode array potentials V_(I) and the dipole densities d_(n),n=1, . . . N of N regions of the cardiac chamber wall; and $\begin{matrix} {W_{k} = {\sum\limits_{l = 1}^{L}{\sum\limits_{n = 1}^{N}{A_{kl}B_{l\; n}{d_{n}.}}}}} & (3) \end{matrix}$ where equation (2) above is substituted into equation (1) to form equation (3).
 17. The system according to claim 16, wherein the dipole density module is configured to solve equations (2) and (3) using regularization techniques.
 18. The system according to claim 17, wherein the regularization technique is Tikhonov regularization.
 19. The system according to claim 2, wherein the system is further configured to: generate a computer display of dipole density information based on the database of dipole densities d(y); and update the computer display of the dipole information based on updating the database of dipole densities d(y).
 20. The system according to claim 2, wherein the database of dipole densities d(y) represents a distribution and activity of dipole charge densities on one or more cardiac wall.
 21. The system according to claim 2, wherein the mapping information recorded from the at least one skin electrode is used to recalculate the database of dipole densities d(y).
 22. The system according to claim 2, wherein the at least one skin electrode comprises more than one skin electrode.
 23. The system according to claim 2, wherein the at least one skin electrode is configured for placement on a thorax. 